我在我們的產品中使用 Akka actor。我們寫了一些代碼：   @Singleton   public class SingletonObj {      private Map<String, Integer> cached = new HashMap();      public void set(String key, Integer value) {         cached.put(key, value);      }      public void delete(String key){         cached.delete(key}      }   }   public class MyActor  extends AbstractActor implements InjectedActorSupport {       @Inject SingletonObj singletonObj;        public static Props props(Injector injector) {        return Props.create(MyActor.class, injector);    }    public MyActor(Injector injector) {        this.injector = injector;        receive(ReceiveBuilder.create()            .match(AddEvent.class, this::addEvent)            .match(DeteteEvent.class, this::deleteEvent))            .build());        }        private void addEvent(AddEvent addEvent) {singletonObj.set(addEvent.key, addEvent.value);}        private void deteleEvent(DeteteEvent event){singletonObj.detele(event.key);}   }   public class Controller {       private Injector injector;       private ActorSystem actorSystem;       public void handleAdd()...       public void handleDelete()...   }然后當我junit為這些課程寫一些測試時   @Test public void testMethod(){       sendAddRequest(...);       sendDeteleRequest(...)       ...       ...       assertThat(singletonObj.get("someString")).isEqual(42)    }那么這個測試是不可靠的，因為當我斷言時，所有事件都沒有被處理。我如何等待 actor 系統中的所有事件完成？